Field of the Invention
The present invention relates to the art of a torque converter having a damping device that suppresses torsional vibrations caused by torque pulse.
Discussion of the Related Art
JP-A-2008-163977 describes a damper device having a double-pinion planetary gear unit for suppressing torsional vibrations disposed between a lockup clutch and a turbine runner. According to the teachings of JP-A-2008-163977, the planetary gear unit comprises a sun gear, a ring gear arranged around the sun gear, first pinion gears meshing with the sun gear, second pinion gears meshing with the ring gear, and a carrier supporting the first and the second pinion gears. In the planetary gear unit, the ring gear is integrated with a disc connected to an outer circumferential portion of the lockup clutch, and the sun gear is integrated with a plate allowed to rotate relatively to the disc through springs arranged in an inner circumferential side of the planetary gear unit. The ring gear is rotated relatively to the sun gear while compressing the springs by pulsation of input torque. Consequently, torque pulse is dumped by an inertia torque of the carrier.
In the damper device taught by JP-A-2008-163977, specifically, springs are arranged between the ring gear and the sun gear, and a relative rotation between the ring gear and the sun gear is caused by pulsation of the input torque. In this situation, the carrier is rotated compulsory and the pulsation of the input torque is damped by an inertia torque of the carrier. However, the damper device taught by JP-A-2008-163977 may be downsized utilizing existing space.